The invention relates to an apparatus according to the patent claims for serially transferring objects between two conveying means. In particular, the invention relates to an apparatus for the type of transfer in which the speed of the supplying conveyor means is larger than or the same as the speed of the receiving conveyor means such that the spacing between the supplied objects is larger than or the same as the spacing between the transferred objects.
Apparatuses of this type are employed for example in the manufacture of can bodies. The rounded bodies prior to welding are ejected from a shaping apparatus and are supplied at a supply speed for transfer. Then they are transferred to a welding station, and advanced through the welding station at a constant welding speed where they are simultaneously welded along axially extending edges. During welding, the bodies are advanced with a very small spacing such that the welding speed is generally smaller than or at most the same as the supply speed. The transfer generally occurs with the aid of a feed cam which engages a body from behind, advances the body over a support surface extending along a transfer strip and there slows down the body whereby the body is overtaken by the conveyor means at the welding station, and the feed cam at its exit point returns to pickup the next body.
Generally the feed cam performs the following movements in each operation:
moving out of an exit position in the space between the last-supplied object and the following object (can bodies), from the side lying opposite the support surface the cam drops into the serially supplied stream of objects, advantageously with a speed parallel to the general conveying direction which is greater than the supply speed; PA1 it picks up the referenced objects still being advanced by the supplying conveying means where it accelerates if necessary; PA1 it overtakes the object from the supplying conveying means where it contacts the object from behind; it advances the overtaken object over a straight transfer strip where it slows down to a transfer speed (welding speed), if necessary after an initial acceleration; PA1 it falls behind the object through further slowdowns where upon reaching the transfer speed the object is overtaken over by transfer conveying means; PA1 it pulls out of the serial stream of objects to the side opposite from the support surface; PA1 it returns outside the serial stream to its starting position.
Since the supply speed is larger than (or at most same as) the transfer speed, upon delivery the spacing between the series of advancing objects, as already mentioned, when supplied is larger than that when overtaken by the transfer conveying means (operating time must be the same). This means that the feed cam must drop out from the series stream faster, that is, with a smaller radius of curvature, than it rises into the stream.
To realize the described operational motions of a feed cam of this type in the prior art, cam drives, cranks with lifting cams or coupling transmissions having a plurality of driven axes were employed, for example. All of these apparatuses are expensive to manufacture and also to operate at high operating speeds.
It is also known that in order to realize a cyclic movement of a feed cam as has been described above, a simple four bar linkage can be employed. However, it is a commonly held opinion that four bar linkages of this type are not suitable for high speeds and for high endurance because of the unavoidable high peak forces. It is a further held opinion that the realization of a special transmission of this type would be very expensive because for its layout a high design and/or experimental expense would be necessary since changes in the transmission parameters and the effect of these changes have no standard simple recognized relationship. For these reasons this type of four bar linkage is generally put aside even though it is likewise known that its manufacture means lower costs than the manufacture of for example a cam drive. A further reason for the limited extension of the four bar linkage to applications such as described above, could be that after its manufacture the four bar linkage is essentially not changeable to achieve its goals.